Rented a designer. Tips for keeping visitors?

Hey, I hired a web designer to overhaul my WP site and I wanted to get some thoughts and ideas on keeping visitors on site and engaged for as long as possible. My plan is to have a great design + great content, but is this the best recipe? What else can I do is keep people on my site? What draws people in?

Post unique contents on site that is the best way. People would like to read what they want to know. Also you can try promotional activities, you can use commercial sites for this.